Mine came from southern Ill and I grew up in SE Iowa but if you brought it here, it'd be a tad further.

What you said is interesting about the clutch valve:

One thing that I noticed was the buzzing noise stopped and the pressure dropped as soon as I pressed the clutch

This should not happen and is contrary to the design. It only vents the engaged clutch and preserves the nominal pressure in the system.

When the clutch pedal is depressed, the clutch
valve lifts, dumping oil from the engaged clutch. The
same motion in the clutch valve seals off passages in
the valve housing, retaining oil supply in valves and in
front of accumulator. The check valve ball also closes
and holds pressure at other end of the circuit.
When the clutch pedal is released again, the clutch
valve drops and oil retained in the valving goes to
work again with only a slight delay.

An even 60 psi at the cooler inlet says (to me anyway ) this cooler - lube circuit is kind of working at it should, though it may not be getting enough flow. If its the pressure regulator valve that's buzzing, the cooler bypass valve seems to be compensating correctly in either pushing the flow to the cooler, or modulating the pulsations produced by the pressure regulator valve slamming back and forth and giving the appearance of a constant pressure at the cooler inlet.

Another valve might be buzzing too. I've been trying to contemplate what might happen if one of the check balls when missing.

On the fun side, I did get to dig a hole with mine yesterday. Didn't get the stump out yet but I made a big mess.

Paul

Mine still doesn't like shifting into low sometimes. With all this great talk on how these things work, I'm going to have to get a pressure gauge on mine just to see what's happening.

Thanks for posting the video Paul. At least I can see how it is supposed to work.
I made a 17 Minute video with my phone yesterday but have yet to upload it to anything.

I went through all the posts Saturday morning and made a list of tests that I thought needed to be done. The top cover was removed. The pressure regulator valve and the clutch valve were out of the bores and both steel lanes were removed when I started. Here are some of the results.

Check bottom of the pressure regulator valve and the clutch lube valve bores for foreign material. I dug around the bores with a hooked piece of wire and found nothing. I blew out the bores with compressed air and dug around some more. No foreign material was present anywhere in the bores.

Check for second “vent” through the clutch lube valve. With the pressure regulator valve in place and the clutch lube valve removed I blew compressed air in the port where the steel line for the clutch lube circuit connects to the case. I then covered the clutch lube valve bore and the vent hole with my fingers and blew again. Air was coming out somewhere lower in the transmission but above the oil level. I then put the clutch lube valve and spring in the bore and was going to hold it down with my fingers while I blew into the steel line port. While getting situated to hold the valve I hit the air nozzle and the valve blew out of the hole. I saw the valve drop into the oil in the case but lost track of the spring. After fishing around in the oil with a magnet I found the valve but not the spring. I had a spring, for a testing purpose, that was similar in strength but shorter, so I put it in with a spacer or shim made from the non-threaded section of bolt. The shim was just long enough to make sure that there was pressure on the spring and the valve was seated, about ¼”. I forgot to test for the second vent with the clutch lube valve in place and I’ll have to order a new spring.

Shim pressure regulator valve and the clutch lube valve and record change in pressure. There were 3 shims in the cap of the pressure regulator valve and I added 2 pennies because I couldn’t find the package of shims. The shim and replacement spring were in the clutch lube bore with the plug installed on top. When I rotated the engine with the starter there was a steady flow of oil coming out of the oil passage for the steel pressure line. The pressure seemed to be higher because the oil stream was 3 or 4 inches longer that previous tests. I attached both steel lines and bolted on the top cover. I left the HLR shifter, steering levers and seat frame off at this time.

With the new pressure gauge attached to the main pressure port, the reverser in neutral and the gearbox in neutral I rotated the engine 3 of 4 revolutions with the starter. The pressure came up to 160 psi without starting the engine and slowly dropped to 0 when the starter was released. When I started the engine, the pressure came up to 170 psi and stayed steady. I couldn’t hear any buzzing, but I was sitting on the hydraulic tank. It ran for about 30 seconds and I shut it down. The pressure stayed steady while running. I thought maybe something I had done fixed the problem, so I attached the levers and seat frame, climbed in and started it again. While I was in the seat I could hear the buzzing and the pressure started to fluctuate and then bounce from 160 psi. to 250 psi. I tried shifting the reverser and the pressure dropped and slowly rose (about 5 seconds) and started bouncing again. With each shift it took longer for the pressure to rise. At that time, I saw some oil on the ground and shut it down. Engine oil was coming from a crease in the oil filter that I created the last time I had the engine out. I had no filter and was done testing for the day.

I got a new engine oil filter yesterday, filled it up with oil and did some more testing.

I was going to see how the pressure would react without shifting the HLR or depressing the clutch. I started the engine with the HLR and gearbox in neutral. The main pressure rose and immediately then the needle started bouncing between 160 and 250 psi. I checked the pressures at the cooler and the inlet was bouncing between 50 and 70 psi. The return line was at 0 and not moving. I let it idle for 3 minutes and 45 seconds and the main pressure continued to bounce from 160 to 250 psi. I decided that was enough time and depressed the clutch and the pressure dropped to 0. When I let the clutch out the pressure steadily rose to 70 psi and the bouncing returned at lower pressures, 70 to 200. When I depressed the clutch pedal about an inch the pressure started dropping and continued to drop the further I pressed and reached 0 psi at the bottom of the stroke. At one point I depressed the pedal about 2” and held there 3 seconds and the pressure dropped to 50 psi and held until I continued to the bottom and the pressure dropped to 0. All these tests were done with the engine clutch still engaged. Disengaging the engine clutch caused the pressure to raise from 0 to 15 psi and return to 0. I could hear the engine pull down when the engine clutch was engaged, and the pressure returned to bouncing 70 to 200 psi.

Shifting the reverser was next. The first shift was from from neutral to reverse. The pressure dropped to about 5 psi and in 6 seconds returned to bouncing 70-200. I shifted multiple times and tried all shifts from hi, low and reverse. The pressure returned every time but with varying time frames. It always rose steady from 0 to 70 psi and then began to bounce. The longest time the pressure remained at 0 then began to rise was 30 seconds.

I agree the shims influenced the main pressure and the clutch valve should not dump the pressure. One of the check balls is supposed to hold the pressure when the clutch valve is raised enough to vent the oil. If that check ball was held off It’s seat that could cause the pressure to drop, but I’m not sure it would be that drastic. Like you said the pump puts out 6 gallons per minute and I don’t think the clutch valve could dump that much.

I got the new spring for the lube bypass valve today.

Last night I tried a shot in the dark. I decided to overfill the transmission to see if the problem could be that the pump was sucking air from inside the case. I added 4 gallons of oil to the transmission and started the machine. The gauge needle was still bouncing just like before.

I’m thinking of draining the transmission to check the screen and filter case again this weekend. This time that I hope I find something in the screen or the bottom of the case that would cause a blockage. If I blow back from the main pressure test point before I drain maybe there will be something there.

On the diagram, it shows the test port as on the shift bypass valve. I am curious if the gauge pulsation is that bypass valve moving from around. Interesting enough, if that valve fails in the closed position, oil would only be entering the clutch engagement circuit (and touching the test port) through the needle valve or via the accumulator side bypass.

On the diagram, it shows the test port as on the shift bypass valve. I am curious if the gauge pulsation is that bypass valve moving from around. Interesting enough, if that valve fails in the closed position, oil would only be entering the clutch engagement circuit (and touching the test port) through the needle valve or via the accumulator side bypass.

I had the same thought when I removed and checked the accumulator housing. I reinstalled and checked the operation with air. There were no pulsations and it seemed to work properly.

Hooked up the air to the main test port in an effort to move whatever debris might be in the system to its furthest point. I then drained the transmission and removed the filter screen looking for anything out of the ordinary. There were a few paint chips, some dirt and some small chunks of the blue silicone that had been used to form the front cover gasket all on the outside of the screen. I poured all of the oil through my wife’s strainer and captured small pieces of the same. There was nothing significant enough to cause a blockage. I hooked the air back up and still nothing.

I changed the air supply to the main supply port on the accumulator housing and attached the pressure gauge to the main test port then tested the clutch valve and HLR clutch operation. The clutch valve didn’t act like it did with the pump oil supply shown in the video. When I pressed the pedal about 1/2” the pressure rose 5 psi and at fully depressed dropped to 50 and held. I did that 3 or 4 times and got the same result. Next I shifted the HLR with the air still attached to the supply port. The correct clutches applied when the shift was made and vented when the rotating valve passed the vents. There did seem to be a lot of air escaping during these tests but the pressures held up well.

I have removed and inspected the clutch valve but the only way to inspect the check ball and its seat is to remove the entire clutch pack. That is a big operation but may be the only one left.
Thanks
Joe

We had storms rolling through yesterday and more coming today. It might be a couple of days before I get back to working on this. I guess pulling the engine, transmission pump and front cover will be the next step.

I got started pulling the engine today. I removed the hard nose and pulled the pressure gauge off of the cooler return line and lowered it in a bucket to drain. Some oil drained out and then I heard something drop into the bucket….an acorn had rolled out of the hose. I then pulled the inlet hose off of the steel line to the transmission and there was another acorn, a bit larger than the steel line, sitting on the opening of the steel line. Both the inlet and return lines had an acorn in them. Funny thing is the closest oak tree is 300 yards away and there are no trees around the loader. I’m wondering if they may have been in there all along.